NoviceSeeker - I understand your point and it is important to look at all the people close to Lindsey, however, I would direct your attention to the affidavit that has been linked several times in the posts above. To me, it is pretty evident that MB is looking for Lindsey. It sounds to me like she is doing something I would do, returning to the scene, night after night, looking for a clue, any clue.
It also seems that her activity is making the No. 1 POI in this case nervous. That's a good thing as long as it does not bring her any harm. I'm a little concerned about that and it is quite possible, LE has told MB for her own safety, maybe not to go looking around.
Salem